REMOTE SENSING APPLICATIONS AND TECHNOLOGIES;
THE AFRICA CHALLENGES
AYADIANI KENNETH RUMI
NIGERIAN METEOROLOGICAL AGENCY,
WEATHER FORECASTING SERVICE, FORECAST OFFICE,
MURTALA MUHAMMED INTERNATIONAL AIRPORT,
IKEJA-LAGOS, NIGERIA
Kenrumi4us@yahoo.com
ABSTRACT
The overall objective of this paper is to assess the imperativeness of the use of Remote
Sensing Applications and Technologies in natural disaster mitigation in Africa with
Nigeria as a case study.
The Meteorological and hydrological hazards which form part of a group of such
increasing devastating phenomena and their major data sources which are not only point
specific but sparse were reviewed. Some guidelines for action as regard the ultimate need
of data with wide aerial coverage of the globe through Remote Sensing coupled with the
pursuit of enhanced capacity building and technology transfer, which will enable early
detection and warning to curb some of these disasters and their perilous socio-economic
implications, are considered prime objectives.
1.0 INTRODUCTION
Over the years, especially during the past four decades, the world has experienced
increasing degree of devastation and insecurity of lives and property by natural disasters
with hydrological and meteorological hazards forming the major part of a group of such
phenomena. Indeed, while no continent of the world is entirely safe from natural
disasters, a large variety of risks and disasters have been particularly severe in Africa.
While the perilous implications of these hazards remain a common factor despite their
variation from one country to another, their non mitigating effects in Africa which result
to lost of lives and livelihood, infrastructure and social destructions, economic
dislocation, as well as environmental degradation are incomparable. Although, while
hazards like tsunami is not quite common and desertification/drought, a slow but gradual
long-term thing, thunderstorms, sand/dust storms, flood and erosion are seasonal
phenomenon.
While it may not be feasible to stop the development of natural phenomenon, Africa
natural disaster mitigation is far from being achieved. This is due to the fact that, in this
era of advanced technology such as high speed computerization that offers the
opportunity for all inclusive large data quality control and assimilation into models that
aid accurate and timely medium and long range forecast, Africa still employ the
conventional method. However, efforts could be made to avoid disaster through the
policies that will not only focus on preparedness, detection mechanism and resources
mobilization but most importantly on mechanisms that reduces vulnerability which will
invariable brings about effective disaster mitigation. And for this to be achieved, the
availability of accurate data, analysis and descriptions of the existing atmospheric
situation with the view to predicting how it will change and move with time is very
essential.
In this respect, the need to intensify existing International cooperation among WMO
member nations for the gathering of up-to-date weather information with wide aerial
coverage larger than the place for which the prediction is required cannot be
overemphasized. This is because as systems move freely across borders or boundaries,
they leave the geographic and political jurisdiction of the originating country and become
the responsibility of another.
Nevertheless, since the employment of polar orbiting and geostationary satellite resources
in the global observing systems especially in filling the gap of inadequacy of data and
their ability to adequately address the problem of existing advanced meteorological
models on global and regional scales in resolving the significant scale phenomena
characteristics of African weather has proved exceptional effective in tracking the
vulnerable systems that ravage Africa, their uses are quite imperative. In this wise,
remote sensing application and technologies coupled with manpower development
through capacity building will indeed go along way to mitigate Africa disaster situation.
2.0 METEOROLOGICAL AND HYDROLOGICAL HAZARDS IN NIGERIA
2.1 LOCATION OF NIGERIA
Nigeria is a country in West Africa and the most populous country on the Africa
continent with The United Nation estimate of 131,530,000 people in 2004. It extends
from the moist tropical zone in the south to the semi-arid savanna zone in the North.
FIG.1
FIG.2
Geo-political zone
States
North Central Zone
Kaduna, Kogi, Plateau. Benue,
Niger, Nasarawa, Kwara
North East Zone
Borno, Yobe, Bauchi,
Taraba, Gombe
Sokoto, Kebbi, Zamfara, Katsina,
Kano, Jigawa
North West Zone
Adamawa,
South East Zone
Abia, Ebonyi, Anambra, Imo,Enugu
South South Zone
Edo, Delta, Rivers, Cross River,
Akwa-Ibim,
South West Zone
Lagos, Ekiti, Osun, Ondo, Oyo,
Ogun
The country is endowed with abundant surface and groundwater resources whose
availability varies with respect to rainfall, location and geological formations. The
highest annual precipitation of about 3,000mm occurs in the Niger Delta and Mangrove
Swamp belt of the southeast where rainfall lasts for almost 10 months of the year.
Rainfall decreases in amount progressively towards the north. The variation in rainfall
also determines the drainage regime in the country
2.2 HAZARDS
As in most other countries of the world particular in Africa, the Nigeria natural disaster
condition today is that of litany of woes with every region having its own share of one
hazard or the other, many of which are linked to meteorological and hydrological
hazards. These range from active sand/dust storms in the northern region to the
devastating thunderstorms activities of the southern region with their attendant
consequences such as desertification and drought, erosion, flooding and land degradation.
2.2.1 Desertification and Drought
Drought and desertification are the most important twin environmental problems
affecting the 15 northernmost states of the country. Drought, a sustained and extensive
regional occurrence of below average natural water availability either in the form of
precipitation, surface water run-off or ground water in this region has been linked to
gradual southward encroachment of the Sahara desert, a process referred to as
desertification.
Desertification is a phenomenon responsible for the lost of about 351,000 square
kilometers of Nigerian land mass and it is advancing southward at the rate of
0.6kilometres per year especially along the Niger Republic border. In the last three
decades, this part of the country has experienced severe droughts notably in 1972-1974
and 1982-1983 with Borno worst hit.
2.2.2 Erosion
While virtually the entire northern region is highly prone to active sand/dust storm
leading to severe wind erosion, thunderstorms often drop excessive rains that lead to
gully erosion.
The wind erosion has been observed to be very severe in the northwestern states of
Sokoto, Kebbi, Zamfara, Katsina, Kano, and Jigawa and two extreme northeastern states
of Yobe and Borno during the winter period of November to February. During this
period, the region, which is under the strong influence of the northeast trade winds
usually referred to hamattan, is characterized by dust haze, which often times remain in
suspension as dust plumes for days in the atmosphere. This situation that often times
extends to the southern region depending on the strength of the wind, has endangered
flight operations. For example, during the case study of 11 December 1998, there were no
flights at all for five days throughout the countries airports amounting to economic loss of
about 5 million dollars (Daily Times, 20 December, 1998).
Gully erosion resulting from runoff of excessive rains of convective instability is
particularly severe in the states of Abia, Imo, Anambra, Enugu, Ondo, Edo, Ebonyi,
Kogi, Adamawa, Delta, Jigawa and Gombe with Anambra and Enugu States alone
accounting for over 50 active gully complexes with some extending over 100 metres
long, 20 meters wide and 15 meters deep.
The coastal areas of Niger Delta and Mangrove Swamp belt of the southeast comprising
of Ogun, Ondo, Delta, Rivers, Bayelsa, Akwa Ibom and Cross River States where rainfall
lasts for almost 10 months of the year are under constant treat of coastal and marine
erosion, the most significant been the overflow of the Bar Beach of the Atlantic Ocean
which has now become a recurrent feature for the past sixteen years.
2.2.3 Flooding
In Nigeria, three main forms of flooding: urban flooding, coastal flooding, and river
flooding have been recorded. Urban flooding which is extensively rampant in Lagos,
Warri, Aba, Benin, Ibadan and Maiduguri is a raining season occurrence in towns located
on flat or low lying terrain especially with little or no provision for surface drainage, or
where existing drainage has been blocked with municipal waste, refuse and eroded soil
sediments. Coastal flooding occurs in the low-lying belt of mangrove and fresh water
swamps along the coast. River flooding occurs in the flood plains of the larger rivers,
while sudden, short-lived flash floods are associated with rivers in the inland areas where
sudden heavy rains can change them into destructive torrents within a short period. In
Nigeria, flash floods from torrential rains have been responsible for the washing away of
thousands of hectares of farmland and dam bursts. For example, 142 people died, 18,000
houses were destroyed and 14,000 farms were swept away when the Bagauda Dam
collapsed following a flash flood in August 1988. Also, urban flooding such as the
Ogunpa disaster which claimed over 200 lives and damaged property worth millions of
Naira in Ibadan, are common occurrence.
2.2.4 Data Acquisition
Despite the havocs wrecking the region due to these meteorological and hydrological
hazards, the sources of data for proper evaluation of their development and movement
remain grossly in adequate. For example, Nigeria which has a vast landmass of some
923,768 km², and a little more than half the size of the U.S. state of Alaska and
comparable in size to Venezuela, can only boost of just about fifty two synoptic stations,
two marine and three upper-air sounding stations are presently functional. The over a
thousand rainfall stations scattered around the country beside been point specific also do
not seem to provide much meaningful impart on the weather prediction of the region
since over seventy per cent are dormant.
Ironically, data with wide aerial coverage of the globe as provided by polar orbiting and
geostationary satellite resources in the global observing systems which act as means of
filling the gap of inadequacy of data and solving the problems arises from the inability of
existing advanced meteorological models on global and regional scales to effectively
track the significant scale phenomena characteristics of African weather are grossly under
utilized. Also the modern Technologies such as high-speed computer machines and the
state of the act telecommunication gargets that facilitate easy dissemination and retrieval
of regional and global data and information are highly inadequate.
3.0 BASIC FORECASTING TOOLS
The African continent being the only continent symmetrically located with respect to the
geographical equator, with most of it lying within the tropical belt is strongly influence
by the two hemispheric anticyclones centered at about latitude 300 North and South of the
equator.
However, the tropical Africa is not without significant influences on its basic air
movement since the extreme northern and southern parts respectively bounded by
moving middle latitude systems. Surrounded by large water bodies (except in the north),
the seasonal heating and cooling of large land masses over continental Africa relative to
the rather minor thermal changes in the surrounding oceanic areas, has resulted to a
seasonal reversal of a large scale flow patterns of wind direction on a continental scale
referred to as monsoons with two kinds of such sub-regional air flow clearly defined (see
FIG.3).
In view of the fact that the pattern over West Africa is comparable to that of well-defined
Indian monsoon, this presentation will concentrate on the West African monsoon, which
is a basic forecasting tool due to its significant role in evolution of weather systems in the
region. However, because tropical systems are notably not well-defined and very elusive
to track in time due to very small pressure changes coupled with scarcity of data,
dynamical studies of such systems are made difficult if not impossible. It is therefore not
surprising that most studies on the mean synoptic features were kinematics that is,
employing the streamline/isotach techniques (Adefolalu, 1978).
3.1 SYNOPTIC CLIMATOLOGY FEATURES OF WEST AFRICA MONSOON
Weather forecasting by climatological approach especially in West Africa has received
wide attention and application. This is because besides the meridional (north-south)
migrations of the sun which is reasonably associated with seasons –DRY (November to
March) during the southward march of the sun in northern winter and WET (April to
October) during its pole ward march in northern summer, the charts (daily, monthly and
even seasonal) have always conspicuously revealed features of planetary scale magnitude
such as the sub-tropical anticyclones and the associated wind pattern (the Trades),
regional phenomena like the Heat Low and waves. Also discernable are features like the
summer tropospheric jets- African easterly jet (AEJ) in the middle troposphere and the
Tropical easterly jet (TEJ) at upper level and the “Gradient level” Trade wind maximal in
winter resulting form the major features.
Besides being useful forecasting tools in their own right, their interactions has great
influences on the monsoonal flow over the region.
As part of an appraisal of the major roles these features play in the evolution of weather
in this region and the need for proper understanding, these features are defined as
follows:
3.1.1 THE SUB-TROPICAL ANTICYCLONE (STA)
A semi-permanent feature, the STA is the most dominant synoptic feature of the tropical
atmosphere from which the northeast trades that prevail through the lower and upper
troposphere in tropical West Africa all year round emanate (see fig.4a). The seasonal
meridional oscillation of its centers has great controlling effect on the three dimensional
structures of the easterlies as well as their intensification and hence the influence of the
monsoons. It is a dynamic High-pressure system that owns its generation and
maintenance to the strong influence of the Tibetan thermal High as proven by the
Numerical; simulation experiments of Krishnamurti et al (1970) (see FIG.4b).
3.1.2 THE TRADES CONFLUENCE ZONES
The climatological and air mass frontal schools of thought in employing the use of largescale features as depicted on mean monthly or seasonal maps, local and diurnal features
associated with geographical and astronomical influences have arrived at the study that
clearly described the monsoon. While the moisture laden and rain bearing southwesterlies
of oceanic origin is described as the summer monsoon, the winter monsoon is better
known as the northeast ‘Trades’ or north easterlies which originate from the sub-tropic of
North Africa usually referred to as “Harmattan” in west Africa. The confluence zone
between these two inter-hemispheric airflow earlier called Inter-Tropical Front (ITF) in a
manner similar to middle latitude front, is better called Inter Tropical Convergence Zone
(ITCZ) in oceanic region and Inter Tropical Discontinuity (ITD) over continental Africa
in view of lack of real weather characteristic of fronts at the surface. The line of
separation, which is usually drawn on the basis of 150C dew point isotherm and wind
field and temperature discontinuity is usually positioned 20Nto 40 N of areas of significant
cloudiness and weather at the surface. At above surface level it is referred to as
Equatorial Trough.
During the northern summer, the ITCZ (ITD) reaches its northern most position at
approximately latitudes 180N – 200N along the coast and 220N –240N inland in
July/August (FIG.5 a). In January, during the northern winter, its southern limit is
attained at approximately latitude 050N – 070N (FIG.5b), the period when almost the
whole West African sub-region experiences the Harmattan dust haze. Figure 6 shows the
mean monthly surface location of the confluence zone along 030E.
Below are the five main zones in relation to the type of air masses after Dhanneur
(1971):
 Zone A, which lies to the north of the ITD is a rainless zone of little high cloud of
cirrus type, is characterized by dry and dusty northeasterly trade winds (the
harmattan) generally light in the mornings, becoming moderate or gusty winds
about mid morning. The relative humidity of usually below 15mb. It is relatively
cool at night with temperature of about 180C – 210C and somewhat hotter during
the day with temperature of about 350C-400C. It is characterized by few days
period of extensive hazy condition resulting from dust plume suspended in the
atmosphere.
 Zone B, which lies to the south of the line of demarcation (i.e. about 2-40N from
of the ITD position) is characterized by a shallow monsoonal flow with variable
meridional extent of between 240-320km; a situation that depends on the season
and value of the element or criteria used in differentiating the air masses. The
conditions are that of a southwesterly wind component generally at night/early
morning and with slightly easterly component early in the afternoon, warmer
nights and somewhat hotter days with temperatures of 210C-240C at night and
daytime temperatures of 290C-320C along the coast and 350C-450C inland. The
weather in this zone is that of characteristic fog or low stratus clouds formation at
night and isolated thunderstorms, which may develop in the afternoon. The total
monthly rainfall is usually less than 76mm.
 Zone C, which is further sub-divided into two zones C1 and C2 lies to the south
of zone B with no well defined boundary as the width is subject to considerable
variation both during the season and from one season to the other. Although the
temperature is much the same as zone B averagely, but the daytime temperatures
vary more and may be higher. It is a zone of maximum monsoonal influences
usually associated with strong convergence with the wind components generally
southwesterly at night/early morning, somewhat freshening in the afternoon and
stronger in C2 than C1.
While C1 is characterized by traversing moving disturbances of Africa such as
synoptic easterly wave, meso-scale line squalls, C2 is the depth of maximum
monsoon influences, which is usually zonal, showing little diurnal variation and
causing heavy rainfall that tends to be more prolong but less intensity. Day
time are relatively cool with temperature range of between 270C – 290C with
night temperature much the same as zone B and C1. The surface wind is usually
south to southwesterly that is much stronger than C1.
 Zone D, which lies to the south of zone C corresponds to air mass from the south,
which is almost homogenous from the surface up to the medium levels covers the
whole of Gulf of Guinea and stretches to about 300-400km out into the ocean.
The zone gives rise to a particular kind of dry season designated as mid-summer
drought or little dry season (Adefolalu, 1973b) in the region lying to the south
09ON in August due to its relatively stable conditions and prevalent temperature
inversion that inhibit upward movement. With relatively dry and cool weather,
temperature ranges between 260C and 300C during the day and about 210C at
night.
3.1.3 THE HEAT LOW
As the sun migrates North – South during the course of the year, the zone of
maximum insulation is easily attained on the continental sub-tropics in summer as the
low heat capacity of the arid land surfaces respond almost immediately than the large
water bodies (which exhibit a lag of about two months). These surface temperatures
maximal are found near latitude 200N in the summer hemisphere. It is also a common
knowledge that the depletion of the ozone layer at lower stratospheric layer (upper
atmosphere) results to minimum temperature at that level. With these effects, while a
lower level pressure minimum is reached at the lowest 2km of the troposphere, a
pressure maximum in the highest part of the troposphere is attained over the subtropical region, a situation that lead to position of maximum temperature almost
coinciding with the low-pressure center with the low center found between latitude
150N to 250N in July hence the term 'Heat Low'.
3.1.4 AFRICAN EASTERLY WAVES
One of the best-known tropical weather systems is the migratory wave-like
perturbations in the mid and lower tropospheric easterlies that organize convection on
large scale. Known as the African easterly waves, they are usually observed during
the summer months (June to October) propagate across North Africa and the Atlantic
Ocean westwards and most times move slowly than the broad easterly current in
which they are embedded. Probably originate west of the Abyssinian high lands in
east Africa; the waves have an average wavelength of 2500km, a period of about 3.5
days and a propagating speed of 8m/s or 7-90.
A vertical cross section of the composite wave near 150N shows the maximum
amplitude of the wind departure, VI of 3.5m/s located at 700mb and extend
downwards to the surface and upwards to 500mb with maximum amplitude of 1m/s
and waves features tilting eastwards thereafter with increasing height but with no
clear evidence of wave activities at 200mb fig.7. This confirms the configuration
depicted on the total flow streamlines and perturbation flow streamlines as shown in
fig.8 and fig.9 where surface convergence (cyclonic) and divergence (anticyclonic)
intensity through well developed 850mb embedded vortex/divergence reaching
maximum at 700mb where the wave structure is distinctly brought out with trough
tilting eastwards. The waves are more pronounced between latitude 090N and 150N.
Over West Africa, the passage of waves has been found to modulate the mean daily
rainfall with its trough region accounting for about 50% at the latitude of maximum
activities.
3.1.5 GRADIENT-LEVEL TRADE-WIND MAXIMA
These are strong winds during the northern winter, which characterize the winter
monsoon. Resulting from the tightening of the meridional pressure gradient at the
surface with speeds of up to 20 – 25 m/sec observed over Sahelian semi-arid zone of
the region especially in Sudan-Tchard area is attributed to either of the following:
(a) The intensification of the Sahara anticyclone cells to the northwest after the
passage of mid-latitude frontal systems (Adefolalu, 1968) (see fig.10a).
(b) The southward extension of the ridge of the Siberia High pressure system from the
northeast corner of Africa (Aina, 1972) (see fig.10b)
3.1.6
THE TROPOSPHERIC JETS
The word jet is loosely used here to distinguish between the characteristic strong
tropospheric easterlies and the otherwise weak easterly current at different levels as
against the acknowledged definition. Two of such wind maxima, the African Easterly
Jet (AEJ) and Tropical Easterly Jet with maximum of up to 12m/sec are known to
influence West Africa atmosphere. While the AEJ which is more of a regional
phenomena whose origin has been traced to the thermal structure over continental
North Africa during summer occurs at between 650mb and 600mb (June –September)
and 700mb (October), the TEJ is an upper level jet at between 200mb-100mb level
usually observed during the peak of summer monsoon in July/August attributed to the
extension of Asiatic Jet at about 200mb that own its development to HimalayanTibetan mountain range.
3.1.5 OCEAN CURRENTS
As in many part of the world, the ocean currents directly and indirectly affect the
weather and climate of West Africa. Over West Africa, a reversed meridional surface
temperature gradient as large as 10C between the center of the heat low and
immediate relatively cooler south have been observed (Burpee, 1972). This situation
is worsen during the middle of the year (July – August) by major upwelling
influenced by cold Benguela current off the west coast of Gulf of Guinea, a period
when the lowest sea surface temperature of about 240C is observed, a situation
responsible for fog and relatively dry weather due to restricting convention
conditions. Besides this cold Benguela current the Guinea current, brings warm water
to the Gulf of Guinea coast, which reinforced the already warm and moist
southwesterly wind for the remaining part of the year.
4.0 CHALLENGES
Over the African continent especially the West African sub-region, the
forecasting techniques described above seems to be the best forecasting
approach despite the fact that climatological studies do not usually provide
accurate daily picture of weather conditions, which are usually associated
with departure from the mean from synoptic disturbances similar in magnitude
to those observed in the middle latitudes.
It is obvious that in the past couple of decades, tremendous breakthrough has
been made especially in the development of advanced global and regional
numerical meteorological models in the temperate region. However, the
existing advanced models on global and regional scales are often times incapable of
adequately resolving the significant small-scale such as cloud clusters,
thunderstorms and squall lines etc which are common features of African
weather. This coupled with the facts that while up-to-date data are available in
Europe, America and Asia due to extensive network of surface observation
and upper-air sounding stations, inadequate data coverage due to sparse network
of station, the absence or inadequacy of telecommunications and
computational facilities in most African countries still remain serious challenge.
Most challenging is the gross under utilization of Polar orbiting and
Geostationary satellites in the global observing systems especially as it
concerns filling the gap of inadequacy of data and their ability to adequately
address the problem of existing advanced meteorological models on global
and regional scales in resolving the significant scale phenomena characteristics
of African weather.
5.0 OCCUPATIONAL FRAMEWORK FOR DISASTER MANAGEMENT
Meteorological and hydrological hazards such as thunderstorms and sandstorms
as they affect Africa continent do not have to become natural disasters. Much
of the risk posed to lives and property can be reduced if proper planning and
proper environment management are put in place.
The application of Remote Sensing and Technology in disaster management
mitigation is indeed a very powerful combination tool for natural disaster
management. Although, in the last few decades, natural disasters have
been on rise both in magnitude and frequency however, the technical capabilities
of this tool to mitigate them have proven successful to a very large extent. These
successes are achieved based on the detailed knowledge of the expected character,
frequency and magnitude of hazards events that constitute such disasters.
The basic occupational framework that make this organizing technologies
successful are in the areas of monitoring, assessment and mitigation:
(i) Monitoring
The use of remote sensing data such as satellite imageries have provided us with the
synoptic overview and useful environmental information with scale ranging from
the entire continent to a few meters. The satellite can detect certain influencing
conditions for the development of many types of hazards that are not revealed by
conventional means of observations. It also makes possible the monitoring of
on- going event while the forces in action are still in full swing.
(ii) Assessment
Assessment in this sense encompasses the finding of the evidence of the impact the
disaster left behind and their interpretation on departure of the disasters, which
provide a quantitative base for relief operations very inevitable. With Remote
Sensing and technologies provided database, coupled with other information,
successful interpretations of the pass occurrences can be made and hazard maps
of potentially dangerous area arrived at. The uses of satellite imagery
and aerial photos also made the opportunity to evaluate or map the variability in
space and time of terrain properties such as vegetation, water and geology
to determine how prone the terrain is to certain hazards.
(iii) Mitigation
Having monitored and assessed stressed above and still the inevitable happens, the
next step is to find solution(s) on how the impacts of the disaster can be
ameliorated or prevented completely in future. With the help of satellite
information, the new situation can be mapped and updated database used for
reconstruction. This will reduce the over dependence on aids from developed
countries.
6.0 GUILDELINES FOR ACTION
One of the basic tools for effective disaster mitigation and reduction is the promotion
of the development and the wider use of earth observation technology to collect data
on environmental imparts, land use and land use changes that will coordination the
global observing systems. Besides their local need, they are also very useful for
integrated scientific assessments such as the global observation research programmes
in view of the need for data sharing among all countries. For Africa to meet up
with this global standard of earth observation that will provide a reliable database
for effective forecasting, the following area must strictly be looked into:
6.1 Improve Observational Networks
Supplementation of the sparse network of observing stations (as it is the case
with Nigeria) with automated telemetry land and ocean-based stations,
measurement from ship platforms and more importantly, the application of
satellite technology. While these additional observations will broaden our
understanding of Africa climate system and its oceanic teleconnections on
real-time bases, the latent knowledge of the initial state of the surrounding
oceans and its continental climate in connection with global climate can be
detected.
With the capacity of satellites to provide data with wide aerial coverage, the
extensive satellites observations of the sub surface ocean conditions and
air-sea interactions in the adjacent tropical Atlantic and Indian oceans will
help improve climate prediction across the region especially as it concerns
seasonal rainfall forecast. Such extensive observational coverage towards Africa
besides improving the insufficient sub-surface data that characterized the
monsoon regions adjacent to Africa, will increase our limited knowledge
of the mechanisms that produces the sea surface temperature (SST) anomalies
in the Atlantic and Indian oceans, eliminate the error from the blended satellite
based SST products and irregular ship reports in cloudy regions outside shipping
route as well as reduces to the bares minimum the complexity of air-sea interaction
that may lead to error in the estimates of fluxes derived from NWP models.
Satellite monitoring and estimate of land surface characteristics such as vegetation
index NDVI and microwave satellite estimate SSMI-derived soil moisture is a
necessity in disaster management. Data derived from these observations will
help in depicting other key land variables such as stream flow, runoff, and surface
heat and radiation budgets.
6.2 Training/ Capacity building
One of the major challenges facing Africa in disaster mitigation and reduction
is in the area of training. As a matter of fact, it is essential to keep a workforce
abreast on what is in vogue in order to advance the course of its organization.
In this regard, the need for international community to maintain its high level of
involvement for the training of meteorologists in advanced numerical and
diagnostic techniques as well as research in the developing world is highly
necessary. Through these intensified training and research projects, necessary
skills to handle the present sophisticated technologies that may in turn lead
to the development of models applicable the region will be acquired.
These training aids, could come inform of international sponsored programmes
(of WMO/UNDP, NWA, European Community etc), regional conferences
and workshops or in conjunction with already existing regional programmes
such as that of African Centre for Meteorological Applications and
Development (ACMAD), Drought Monitory Centres (DMC), conferences with
African Meteorological Society etc through the exchange of expertise. This will
no doubt enhance capacity building of professionals and researchers that can be
relied upon for accurate exchange of data.
FIGURE LEGEND
Figure
1
Legend
Location of Nigeria
2
Map of Nigeria
3
The general features associated with seasonal air mass flow
pattern over Africa
4a & b
Mean velocity potentials and streamline pattern over the
monsoon Afro-Asian region (After Krishna murti et al, 1970)
5a & b
The mean boundary positions of ITCZ (ITD) and
association weather zones in (a) July & (b) January over
West Africa (After Walker)
6
Mean monthly surface location of ITD along
Longitude 030E
7
Vertical cross section of VI (m/s) for an idealized wave (After
Burpee, 1975)
8
Streamline analysis of total wind field associated at
surface, 850mb, 700mb and 200mb
9
Streamline analysis of the departure of the wind field associated
at surface, 850mb, 700mb and 200mb
10a & b
Intensification of the sub-tropical High and tightening of
Pressure gradient the { (a) Sahara anticyclone cells in December)
(b) Siberia High pressure system in January} in relation to middle
Latitude front passage
TABLE:
Geo-political zones and their constituent states of Nigeria
REFERENCES
Adefolalu, D. O., 1972: On mean equivalent potential temperature and the little dry
season over West Africa. Q. Meteorol. Mag., 2, Meteorol. Dept.
Lagos.
1973a: On the mean low level synoptic features over West Africa
during northern summer. QMM. Vol.3, No.3, Sept. 1973 pp
83-94.
1973b: Further studies on the December 1973 pp 110-118.
1974: On scale interaction and the lower troposheric summer easterly
perturbation in tropical
West Africa. Ph.D.
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FIG 4b
FIG.9